Well I finally got around to replacing the slave and replacing the pushrod with one from Rosehill.
Rosehill Performance Parts
Much better than the cut off bolt and washers that were originally used by Backdraft. Mick was right, the end of the bolt wore down and slipped over. Also it need more adjusting out which I couldn't do with the threads on the old rod all mashed down. The slave over entended and the piston came out.
Works great now.